1. Field of the Invention
This invention relates to computer interfaces, and more particularly to a gesture control system for improved drag operation of a pointing device used with a graphical user interface.
2. Description of Related Art
Graphical user interfaces ("GUIs") typically use a pointing device (such as a mouse, light pen, or stylus on a touch-sensitive display screen) to select an object (e.g., text, figures, areas of a display screen, files, folders or directories, object tools, parts of figures or other objects such as vertices and edges, etc.) under a cursor and then "drag" the selected object to a different location or orientation on a display screen. The user may then "drop" or release the object at a desired new location or orientation indicated by the position of the cursor.
Selecting is usually a first step, generally initiated by holding down a button associated with the pointing device (e.g., a mouse button) and gesturing with the pointing device to indicate the bounds of the object to be selected (as in text selection), or simply by "clicking" on the object under the cursor (as in selecting a graphical image or icon). Selection is typically indicated by a change in the visual display of the selected object (e.g., by using reverse video, displaying a frame around the object, displaying selection handles around the object, etc.).
Dragging is usually a separate step distinct from selection, and is usually initiated by clicking on a selected object and holding a control button down (e.g., holding a mouse button in a depressed state). The object is then dragged while holding the control button.
However, in some applications, initiating dragging also selects the object under the cursor. The operation is completed by dropping the selected object.
For many applications, a drag operation may be used to initiate several possible functions relative to an object. For example, in a text application, a selected section of text may be moved or copied by a drag operation. As another example, in a page layout program such as Adobe Framemaker.RTM., a selected file may be inserted into a document by embedding (i.e., copying the content of the object), by linking (i.e., referencing the content of the object such that changes to the original appear in the linking document), or by reference (e.g., establishing a hypertext link to the object).
Normally, if multiple functions are possible, one such function (e.g., moving) is a "default" function of a drag operation, while the other functions must be selected by some combination of modifiers (e.g., pressing keys like "SHIFT", "ALT", and "CTRL") while operating the pointing device. However, there are a finite number of such combinations available, and none are particularly intuitive. Indeed, some applications have adopted contrary or confusing combinations. For example, in Microsoft Windows95.RTM., dragging a file object to a directory icon on the same storage device initiates a MOVE function by default, but can be changed to a COPY function if the CTRL key is pressed before dropping the file object. However, dragging a file object to a directory icon on a different storage device initiates a COPY function by default, but can be changed to a MOVE function if the SHIFT key is pressed before dropping the file object.
In some applications, after completing the drag operation, a menu automatically pops up to allow a user to choose a specific "drop" function. However, such menus do not allow changing the nature of the drag operation before dropping.
Accordingly, the inventor has concluded that it would be desirable if a more intuitive method and system existed for selecting among multiple functions during a drag operation, allowing a user to change a gesture after it has begun. The present invention provides such a method and system.